The PhD defence and trial lecture will be held in Auditorium 1 in The Geology Building. In some cases, it will be possible to attend the trial lecture and dissertation digitally, in that case a link to Zoom will be posted.
Trial lecture
Wednesday 13 May, 10:15-11:00, Aud 2, The Geology Building:
Potential diversity of rocky planet atmospheres from a Solar System and first principles perspective
Conferral summary
Red dwarfs are the most common stars in the Milky Way and host the most known Earth-like planets in habitable zones. In their youth, they produce frequent and powerful flares that subject nearby planets to intense ultraviolet radiation. This work investigates whether a primordial planetary atmosphere can survive long enough under such conditions for water to persist and life to arise. The research shows that the rotation period is a better indicator of activity level than the age of the star. The YMDF model was then developed to reproduce the time evolution of the spectra of active young M stars. The results show that water and hydrogen, being the dominant species, are preserved in most parts of the atmospheric column, even during intense stellar storms over the one-year simulation time, and that vapour-dominated atmospheres can maintain water as the stars mature.
Main research findings
Popular scientific article about Mamonova’s dissertation:
Life Under Fire: Planets Around Young Stars
Red dwarf stars, the most common stars in the Galaxy, are magnetically violent in their youth, producing frequent powerful flares that bombard nearby planets with intense ultraviolet radiation. They also host the majority of Earth-sized planets in potentially habitable zones. The central question of this work by Elena Mamonova is whether, in a planetary atmosphere, water can survive long enough under such conditions for life to ever emerge.
To answer this, the flaring behaviour of young red dwarfs was first characterised using young stars in known star-forming regions, revealing that rotation period is a better predictor of flare activity than stellar age, and that a piecewise power law accurately describes flare frequency distributions. Building on this, E. Mamonova developed the Young M Dwarf Flare model, combining radiative-hydrodynamic stellar atmosphere models with high- and low-energy electron beam simulations to reproduce the time-dependent spectra of flaring young red dwarfs, validated against both solar and stellar observations.
Applying this model to simulate one year of atmospheric chemistry kinetics on young Earth-like planets shows that dominant species such as water and hydrogen are preserved throughout most of the atmospheric column by self-shielding, even under intense flaring. In steam-rich atmospheres, photochemistry produces up to ten per cent oxygen through chemistry alone, with no life involved. Regardless of planet size, the water is retained in such atmospheres, suggesting that these worlds could preserve liquid water reservoirs at the surface as their host stars mature. In young systems, mini-Neptune atmospheres can be observable with the James Webb Space Telescope and offer the nearest opportunity to test these predictions, particularly through observation of atmospheric water features.
Photo and other information:
Press photo: Elena Mamonova, portrait; 1000px. Photo: Private
Other photo material: Illustration with description and credit as specified in the article above, size 1200px.
